A DC/DC voltage regulator is operative to maintain a level output voltage despite variations in power supply voltage or current drawn by a load. Many portable devices require a steady voltage supply such as that provided by a DC/DC voltage regulator. Switch mode regulators can be subject to a phenomenon of current ratcheting at shorted loads due to finite on times to determine an over current condition. Nearly every switch-mode device has a finite loop response time to measure current in the inductor. Depending on the input voltage, the current can rise high enough to cause a catastrophic failure in a device.
For this reason, in fixed frequency parts, it is common to use frequency fold-back to change the amount of current ratcheting that a part can see. A common problem caused by frequency fold-back is a large current ripple in the inductor. For this reason, a larger than normal bypass or output capacitor is chosen to reduce the ripple voltage. And if the frequency is folded back too much, the loop may become unstable. Thus, choosing the correct fold-back frequency range for wide application is not an easy task.